Hydrogen peroxide containing solutions are used in various processes for the dissolution of metals and metal oxides. Examples of such processes included pickling, bright dipping, pre-etching, etching, manufacture of filaments for light bulbs etc. Hydrogen peroxide, which is added to the acid treatment solutions for the purpose of promoting the disolution and/or to prevent the formation of toxic fumes during the dissolution, is consumed in these processes and has to be replenished at least on a periodic basis to maintain its concentration in the treatment solution within the effective range. Some of the heavy metals, most notably iron and copper, cause an instability of the hydrogen peroxide in solution, expecially as these heavy metal ions accumulate during use. A rapid catalytic decomposition of the hydrogen peroxide not related to its consumption during processing occurs, resulting in excessive quantities of hydrogen peroxide being lost from the processing solution. In the past, various stabilizers have been added to hydrogen peroxide to protect it from decomposition in storage and shipping from trace quantities of these metals. Other stabilizers have been formulated to stabilize the hydrogen peroxide content of metal processing solutions. Compounds such as low molecular weight carboxylic acids and alcohols have been shown to have a retarding effect of hydrogen peroxide composition. Other known inhibitors include glycerine, glycols, polyglycols, phenol, p-methoxy phenol, alkyl and aryl sulphonic acids, sulfathiazole, phenacetin, 9-hydroxy quinoline, urea and amino pyridine. In general, the above mentioned hydrogen peroxide stabilizers have not been entirely satisfactory, for various reasons, such as insufficient stability at elevated process temperatures, obnoxious odors, excessive volatility, problems of undesirable side reactions with metal ions causing the formation of insoluble by-products, high costs, toxicity, etc.
It is therefore a primary object of the present invention to provide a new and improved metal dissolution process solution containing hydrogen peroxide stabilized against decomposition by the dissolved heavy metals contained therein. Another object is to provide a method for stabilizing hydrogen peroxide solutions against the degrading effect by heavy metal ions. Still another object is to provide a novel process for the pickling of copper and copper alloys.
Other objects will become readily apparent from a reading of the specification and appended claims.